A prior art locking valve for use primarily with hydraulic cylinders is illustrated in a catalog titled Hydraulic and Pneumatic Check and Relief Check Valves published by Kepner Products Co., Villa Park, Ill. Those prior art locking valves are pilot operated such that release of the locking valves requires application of fluid pressure to a pilot port of the locking valve. Such locking valves do not permit release of the locking valve in the absence of a fluid pressure source.
A prior art flow-control valve for use primarily with pneumatic cylinders is illustrated in a catalog published by Legris, Inc., Rochester, N.Y.
Attention is also directed to the following U.S. patents:
______________________________________ NAME U.S. PAT. NO. ISSUE DATE ______________________________________ Kepner 2,959,188 11/8/60 Kepner 3,335,750 8/15/67 Kaetterhenry 4,018,136 4/19/77 Panis 3,975,987 8/24/76 Gerulis 4,192,338 3/11/80 Bobnar 4,172,582 10/30/79 Bitonti 3,980,336 9/14/76 Martin 3,817,154 6/18/75 Parrett et al. 3,792,715 2/19/74 Reith 4,531,449 7/30/85 Bingel 3,229,721 1/18/66 ______________________________________